The chassis looks great, and again, kudos on putting in all the extra work to etch your own board! I'm looking forward to hearing your impressions.

I recently took a few more measurements of my NTD1 using a separate outboard ADC and patching it digitally into the AP. This allows more accurate measurements as the outboard ADC has much lower distortion than the internal one on the AP.

As I always suspected, distortion is significantly lower than originally measured.

1. DPR @ -4dBFS - 2nd and 3rd harmonics are down 131dB and 127dB respectively
2. DPR @ -6dBFS - 2nd and 3rd harmonics are down 131dB and 133dB respectively
3. FFT of the output @ -6dBFS. Scale the whole thing up by 12dB if you want values in dBV. This puts the noise floor at between -138dB and -158dB!
4. THD vs. Freq @ -6dBFS. Values below 10Hz and above 7kHz are not valid due to high and low pass noise filters at 20Hz and 22kHz.

Great distortion figures. But I'm not too nervous about perfect tech specs. My Aleph30 clone made years ago is still one of my preferred amp, and doesn't test so great. I have a CLIO analysis system and I'll certainly have a look at the specs, but I'll be happy if the dac sounds just great

With distortion levels so low from source to output tweaks are audible ,this one
seems to be a positive one to my ears.

My NTD1 Bll combo does not suffer from what I call "digitosis"...you know the junk that makes some of Madeleine Peyroux's recordings fatiguing and sends your tweeters into fits on a most digital systems. I think reviewers call it "glare" Well the glare is gone! Analog tone with digital detail.

1. The gate voltage is not what you should be measuring! You need to adjust the pots to measure 1.65VDC on the SOURCE of the mosfet (where the DAC outputs connect to) relative to GND.

2. The protection zener diodes were incorrect on the PCB. This error has been covered several times throughout the thread, but it's easy to miss. If you want to keep the protection zeners, you need to make a little tee-pee putting two zeneres back to back on the same pad. There are instructions in the thread somewhere with pictures.

Fix the above two things, and you should be good to go. Do not attach the DAC to the I/V stage until you've got the proper 1.65VDC at the source of each fet! If you have a high voltage there, you could damage the DAC.

thats my fault, I mispoke in my instructions as we had been just talking about gates, so i had gated head; but we corrected that straight away in the subsequent posts. maybe i should get the mods to correct my first post?